Optimisation of the Adhesion of Polypropylene-Based Materials during Extrusion-Based Additive Manufacturing

Abstract

Polypropylene (PP) parts produced by means of extrusion-based additive manufacturing, also known as fused filament fabrication, are prone to detaching from the build platform due to their strong tendency to shrink and warp. Apart from incorporating high volume fractions of fillers, one approach to mitigate this issue is to improve the adhesion between the first deposited layer and the build platform. However, a major challenge for PP is the lack of adhesion on standard platform materials, as well as a high risk of welding on PP-based platform materials. This study reports the material selection of build platform alternatives based on contact angle measurements. The adhesion forces, investigated by shear-off measurements, between PP-based filaments and the most promising platform material, an ultra-high-molecular-weight polyethylene (UHMW-PE), were optimised by a thorough parametric study. Higher adhesion forces were measured by increasing the platform and extrusion temperatures, increasing the flow rate and decreasing the thickness of the first layer. Apart from changes in printer settings, an increased surface roughness of the UHMW-PE platform led to a sufficient, weld-free adhesion for large-area parts of PP-based filaments, due to improved wetting, mechanical interlockings, and an increased surface area between the two materials in contact.

Material extrusion‐based additive manufacturing of polypropylene: A review on how to improve dimensional inaccuracy and warpage

“…Several individual research groups discovered that the first layer adhesion to the build platform is one of the main process limitations of PP . It was found that PP does not adhere to standard ME‐AM build platform substrates, such as glass mirrors or polyimide tapes, mainly due to the material's lack of surface functional groups, low surface energy, and low polarity .…”

“…It was found that PP does not adhere to standard ME‐AM build platform substrates, such as glass mirrors or polyimide tapes, mainly due to the material's lack of surface functional groups, low surface energy, and low polarity . In order to counteract a possible delamination of the first deposited layer, most researchers recommend to deposit PP‐based filaments onto PP substrates . However, special care needs to be taken in order not to weld the first deposited layer onto the PP build platform, which can lead to a complete damage of the 3D‐printed component during part removal.…”

“…Strategies to counteract this issue address the choice of build platforms with a slightly different surface energy as well as polarity but similar chemical composition. Recommended platform materials for successful 3D‐printing PP include random PP copolymers or UHMWPE …”

“…As a result, the production of the final part cannot be continued flawlessly. If the adhesion is too good, especially at room temperature, the final product cannot be removed from the platform without damaging the part, the platform, or both . In an ideal process, the part is processed at high adhesion between the first layer and the platform, controllable, for example, through the temperature of the build platform, whereas the part removal is conducted at a state of low adhesion .…”

Impact Optimization of 3D‐Printed Poly(methyl methacrylate) for Cranial Implants

“…In contrast to semi-crystalline 3D-printed materials, where shrinkage can be a severe issue, [45][46][47][48] no warpage of the 3D-printed specimens was observed, as long as sufficient first layer adhesion was guaranteed. [27,49] Therefore, the adhesive spray Dimafix (DIMA 3D, Spain) was applied to the glass mirror. Five specimens were produced per print.…”